Our overall objectives are to elucidate the pathways by which two specific intracellular polysaccharides (glycogen and mycodextran) are synthesized and degraded by filamentous fungi, and the mechanisms by which these pathways are regulated. Our research will include the purification and characterization of several key enzymes of the glycogen cycle from Neurospora crassa, including: glycogen phosphorylase b and a, phoshorylase b kinase, phosphorylase a phosphatase, a cyclic AMP-dependent protein kinase, and two forms of glycogen synthetase. Mycodextran (Nigeran) is a linear polysaccharide composed of alternating alpha-1,4 and alpha-1,3 linked glucose residues. The polysaccharide is accumulated by many Penicillium and Aspergillus species under conditions of low pH and nitrogen deficiency. We hope to establish (a) the cellular location of the accumulated polymer, (b) the enzymes involved in its biosynthesis, and (c) the relationship between the physiological conditions favoring mycodextran accumulation and the activity and levels of the enzymes involved. Standard techniques of protein chemistry and enzymology will be employed.